Sadly I don't think large plate exists, I had never even seen large studded leather armor until a few days ago (also found out I could use the underground rail system in tarant, I beat myself sensles after figuring it out, I've had the game for a damn YEAR!) And I'm pretty sure blessings can let you go above the max if you are already there.
You can find large plate late in the game. It's been so long since I played the game that I don't remember the specifics, though. But anyway, it's in that town where you can buy a ship (Dernholm?). Later on in the game you go to the bar where you get the Stringy Pete quest and there should be a couple of ogres wearing large plate guarding some dude. You can kill them for it or maybe use a fate point. I'm not sure if it's possible to steal something that's equipped, though. Also, I'm pretty sure that blessings can NOT let you surpass racial maxes. You'd figure that a God's blessing would let you be stronger or smarter than possible, but... nope.
There is some Poisioned Plate you find through a quest in Caladon. It fits large folk & with the amulett you get on the Isle of Dispiar.... A fate point will get the large plate off the gaurds in the bar, so will Dominate Will.
Answer: NO. Unless u already have a bonus as a result of a background or race, I don't think there is a way. However, if you acquire a title when under influence of the blessing, it will stay there(but not what the blessing adds)